Apparatuses for stent shaping

ABSTRACT

An apparatus for crimping a radially expandable stent includes a pressure vessel, shaping balloon, and mandrel. The mandrel is configured to slidingly receive a stent thereon, and to be slidingly advanced into the pressure vessel. The shaping balloon is inflated to radially compress the stent onto the form of the mandrel; such compression need not be uniform. Pressurization of the shaping balloon facilitates the expansion of the balloon to achieve compression of the stent, with depressurization of the shaping balloon causing the balloon to return to an unexpanded state.

RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.15/880,392, filed Jan. 25, 2018, now issued as U.S. Pat. No. 10,537,929,which is a continuation of U.S. application Ser. No. 15/254,955, filedSep. 1, 2016, now issued as U.S. Pat. No. 9,889,487, which is adivisional of U.S. application Ser. No. 13/675,678, filed Nov. 13, 2012,now issued as U.S. Pat. No. 9,433,991, which claims priority under 35U.S.C. § 119(e) to U.S. Provisional Application No. 61/578,764, filedDec. 21, 2011, the entire disclosure of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus used to shapestents, particularly those used for medical devices. More specifically,the present invention relates to methods and apparatus for pneumaticallyand/or hydraulically shaping stents and similar structures, includingdevices having stents for support.

BACKGROUND OF THE INVENTION

The term “stent” is generally used to refer to medical devices and/orsupports therefore which can be implanted in anatomical passageways(e.g., blood vessels, valve annuluses, body ducts, etc.) of the body forthe purpose of maintaining the patency or state of dilation of thepassageway, reinforcing the passageway, or anchoring a valve or graft orother object within the passageway. For purposes of this application,the term “stent” is used to refer to such supports, including supportsintended for radial expansion as well as supports which are not intendedfor radial expansion.

Many stents are not intended for delivery and subsequent expansion viacatheter, but are instead delivered and deployed in their full form andshape. Examples of such stents include supports for surgical heartvalves and grafts. Stents for delivery via catheterization may beinitially disposed in a compact configuration of relatively smalldiameter upon or within a delivery catheter to facilitate insertion andadvancement of the stent into a desired anatomical passageway. Once atthe implantation site, such stents may be radially expanded to a largerdiameter which is equal to or slightly larger than the diameter of theanatomical passageway in which the stent is to be implanted. Whenradially expanded to the larger diameter, the stent may be released fromthe delivery catheter, and left in place where it is anchored (e.g., viafrictional engagement) to the surrounding wall of the anatomicalpassageway.

In general, expandable stents fall into two major categories: a)self-expanding and b) balloon-expandable. Self-expanding stents may beformed of resilient or shape memory material (e.g., spring steel ornitinol) which is capable of self-expanding from a relatively smalldelivery diameter to a larger deployed diameter, with the expansionbeing achieved by releasing the stent from its compressed configurationwhereupon it expands to its larger diameter in spring-like fashion.Balloon-expandable stents may be formed of plastically deformablematerial (e.g., stainless steel) which can be radially expanded byinflating a balloon positioned within inner lumen of the stent.

Stents can be provided in various sizes and shapes. Many stents aresimple cylindrical forms and have substantially constant diameters alongtheir lengths. However, for some applications it may be desirable for astent having a more complex shape, including shapes where the diameterof the stent varies substantially along the length of the stent.

Stent shapes can be defined using various techniques. One common devicefor shaping stents is a crimper. Current stent crimpers tend to bepurely mechanized devices that crimp stent frames into basic geometricshapes such as constant-diameter cylinders and simple cones. They haverelatively complex mechanisms but are limited to forming relativelysimple shapes.

What are needed are crimping devices and methods for forming stents incomplex shapes using a relatively simple forming mechanism. The currentinvention meets these needs.

SUMMARY OF THE INVENTION

An apparatus for shaping stents includes a pressure vessel and mandrel.The pressure vessel has an upper plate with an upper plate opening, alower plate with a lower plate opening, and a central plate assemblywith a central plate and central plate opening. The central plateassembly includes a shaping balloon defining a balloon interior chamber,with the shaping balloon passing around the inner perimeter of thecentral plate opening and forming a balloon central opening in theradial center of the shaping balloon. The shaping balloon has aninflated configuration and a deflated configuration. The upper plate andlower plate and central plate are stacked together, with the centralplate positioned between the upper plate and the lower plate. When theplates are thus stacked, the lower plate opening, upper plate opening,and balloon central opening form a continuous mandrel-receiving lumen.

The apparatus also includes a mandrel sized and configured to beadvanced along its longitudinal axis into the mandrel-receiving lumen ofthe pressure vessel. The mandrel has an upper mandrel plate, a lowermandrel plate, and a central mandrel portion. The upper mandrel platehas a shape configured to fit tightly into the upper frame plateopening, and the lower mandrel plate has a shape configured to fittightly into the lower frame plate opening. The central mandrel portionhas a shape corresponding to a desired stent shape, wherein the mandrelis sized and configured to be slidingly advanced along its longitudinalaxis into the mandrel-receiving lumen.

The central plate assembly may have a fluid lumen in fluid communicationwith the balloon interior chamber. Fluid can be provided into the fluidlumen to inflate the balloon, and the fluid can also be removed throughthe fluid lumen to deflate the balloon. The fluid lumen may passradially through a portion of the central plate. The fluid lumenincludes an open end which communicates with the exterior of theapparatus. The pressurization of the balloon interior chamber via thefluid lumen facilitates the uniform compression of the shaping balloon,with the depressurization of the balloon interior chamber via the fluidlumen being operational to allow the shaping balloon to return to anuncompressed/unexpanded state.

The upper mandrel portion may have an upper diameter, with the lowermandrel portion having a lower diameter. The upper diameter may be thesame as, or different from, the lower diameter. The central mandrelportion defines a stent-receiving area having one or more areas ofreduced radial diameter, wherein the one or more areas of reduced radialdiameter are smaller in (i.e., reduced in) diameter than at least one ofthe upper diameter or lower diameter. The area of reduced radialdiameter may be smaller in diameter than both the upper diameter andlower diameter. The stent-receiving area may have a substantiallytubular shape with a substantially constant diameter along alongitudinal length thereof. The stent-receiving area may have asubstantially tubular shape having varying diameters along alongitudinal length thereof. For a mandrel for use in shaping aprosthetic heart valve stent, the varying diameters may be between about15 mm and 35 mm, with longitudinal lengths which may be about 8 mm to 40mm. Diameters of 20 mm to 30 mm (which may be constant or varying alongthe length of the mandrel) are also within the scope of the invention,as are lengths of 8 mm to 10 mm.

A stent may be positioned on the stent-receiving area of the mandrel.The stent may be formed from biocompatible material, such as stainlesssteel or shape-memory material (e.g., nitinol), and may have asubstantially open mesh-like portion. The stent-receiving portion of themandrel may have an outer surface which is formed from substantiallyflexible material, which can provide padding to cushion the stent as itis compressed against the mandrel. The mandrel may have an inner shapewhich is formed from substantially rigid, non-deformable material. Witha substantially flexible coating on the inner shape, the stent can becompressed to form the desired shape of the rigid inner shape whilestill having some padding provided by the outer surface. The upperand/or lower mandrel portions may be configured to be releasablyattached and re-attached to the central mandrel portion.

The stent-receiving portion of the mandrel may have heating and/orcooling capabilities, which can assist in setting the shape of ashape-memory stent such as a nitinol stent. The stent-receiving portionmay include one or more heating elements, such as resistive heaters, toraise the temperature to a desired temperature.

The shaping balloon may be formed of substantially flexible andelastomeric material, or can be formed of flexible but substantiallynon-elastic material. The shaping balloon in its expanded configurationmay form a pre-defined shape wherein the balloon central opening has asubstantially continuous inner diameter, or may form a pre-defined shapewherein the balloon central opening has a substantially tubular shapehaving varying internal diameters along a longitudinal length thereof.

The shaping balloon may have an upper edge and a lower edge, with theupper edge of the shaping balloon sandwiched between an upper surface ofthe central plate and a lower surface of the upper plate, and the loweredge of the shaping balloon sandwiched between a lower surface of thecentral plate and an upper surface of the lower plate.

Methods of shaping a stent according to embodiments of the invention mayinclude providing a pressure vessel, with the pressure vessel having apressure vessel lumen, the pressure vessel further having a shapingballoon positioned circumferentially about the pressure vessel lumen anddefining an central inner wall portion of the pressure vessel lumen. Theshaping balloon may have a balloon opening and a balloon interiorchamber, with the balloon opening defining a central lumen portion ofthe pressure vessel lumen, the pressure vessel further having a fluidlumen in fluid communication with the balloon interior chamber. A methodmay further include providing a mandrel with a stent-receiving portion,with the mandrel sized and configured to be slidingly advanced into thepressure vessel lumen to a position where the stent-receiving portion ispositioned within the balloon opening. The method may includepositioning a stent onto the stent-receiving portion of the mandrel,slidingly advancing the mandrel into the pressure vessel lumen to aposition where the stent-receiving portion is positioned within theballoon opening, inflating the shaping balloon with sufficient pressureto cause the balloon to expand to its expanded configuration, wherebythe balloon compresses against the stent to compress the stent onto thestent-receiving portion of the mandrel, whereby the stent conforms toand assumes the shape of the stent-receiving portion of the mandrel, anddeflating the shaping balloon. The method may further includewithdrawing the mandrel from the pressure vessel lumen, and removing thestent from the mandrel.

The mandrel may have a releasable end (upper and/or lower) configured tobe removed and re-attached to the stent-receiving portion, wherepositioning the stent onto the stent-receiving portion involves removingthe releasable end, slidingly advancing the stent onto thestent-receiving portion, and re-attaching the releasable end. The stentmay be formed of stainless steel, and removing the stent from themandrel may involve removing the releasable end, slidingly removing thestent from the stent-receiving portion, and re-attaching the releasableend. The stent may be formed of a shape memory material such as nitinol,and the method may involve, after or during the step of inflating theshaping balloon with sufficient pressure to cause the shaping balloon toexpand to its expanded configuration, but prior to deflating the shapingballoon, the further step of exposing the stent to a desiredshape-setting temperature, followed by exposing the stent to a desiredreduced temperature. Exposing the stent to the desired shape-settingtemperature may include adding to the balloon interior chamber a fluidhaving a temperature that is at or above the desired shape-settingtemperature. Exposing the stent to the lower temperature may includeadding to the balloon interior chamber a fluid having a temperature thatis at or below the desired shape-setting temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become appreciatedas the same become better understood with reference to thespecification, claims, and appended drawings wherein:

FIGS. 1A and 1B depict side and bottom views of a stent having a complexform capable of being produced using the methods and devices ofembodiments of the invention;

FIGS. 2A-2E depict a perspective (cross-section), side (cross-section),top, top (with top plate removed), and bottom views of an apparatusaccording to an embodiment of the invention;

FIG. 3 depicts a side view (cross-sectional) of a pressure vesselaccording to an embodiment of the invention;

FIGS. 4A-4E depict side views (cross-sectional) of mandrels according tovarious embodiments of the invention;

FIG. 5 depicts a side view (cross-sectional) of a mandrel with stentpositioned thereon according to an embodiment of the invention;

FIG. 6 depicts a side (cross-sectional) view of the mandrel and stent ofFIG. 5 positioned within a pressure vessel with the shaping balloondeflated according to an embodiment of the invention;

FIG. 7 depicts a side (cross-sectional) view of the mandrel and stentpositioned within the pressure vessel of FIG. 6 but with the shapingballoon inflated according to an embodiment of the invention;

FIGS. 8A and 8B depict side views, assembled and exploded, of a mandrelwith detachable upper and lower portions;

FIG. 9 depicts a side view, in cross-section, of a mandrel having aresilient coating and a heating element according to embodiments of theinvention; and

FIGS. 10A and 10B depict side views, in cross-section, of a pressurevessel and shaping balloon according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIGS. 1A-1B, a stent 10 is depicted having a loweropening 12, an upper opening 14, a stent lumen 16, and a main stent body18. A mesh-like structure forms the stent wall 20. The main stent body18 has a relatively complex form, where the inner diameter varies alongthe length 24 of the stent 10. At the lower opening 12, the innerdiameter 22 _(lower) is relatively large, but the inner diameter variesalong the length and reaches a relatively small inner diameter 22_(upper) at the upper opening 14.

A stent shaping apparatus 30 according to an embodiment of the inventionis depicted in FIGS. 2A-2E. The apparatus 30 has a mandrel 32 having alower portion 34 with a lower diameter 36, an upper portion 38 with anupper diameter 40, and a central stent-supporting portion 42 having avarying diameter profile portion 44. The largest diameter 46 of thevarying diameter profile portion 44 is less than the upper diameter 40and also less than the lower diameter 36 so that a stent may be mountedthereon and still have, even prior to full compression, an overall outerdiameter smaller than the upper diameter 38 and lower diameter 36 of themandrel 32 in order to facilitate positioning of the mandrel and stentinto the pressure vessel 50.

The pressure vessel 50 has an upper plate 52 having an upper opening 54,a lower plate 56 having a lower opening 58, and a central plate 60having a central opening 62. A substantially ring-shaped shaping balloon64 is positioned within the central opening 62, with an inner opening 66defined within the shaping balloon 64. The upper opening 54, inneropening 66, and lower opening 58 are in longitudinal alignment anddefine a pressure vessel central lumen 68. The pressure vessel centrallumen 68 is sized and configured to slidingly receive the mandrel 32therein. The entire pressure vessel assembly 50 may be held together viascrews/bolts 71.

The upper diameter 40 of the mandrel 32 is about the same size as thediameter of the upper opening 54 of the pressure vessel 50. Similarly,the lower diameter 36 of the mandrel 32 is about the same size as thediameter of the lower opening 58 of the pressure vessel 50. With thissizing and configuration of the upper and lower mandrel portions 38, 34largely matching the size and shape of the pressure vessel upper andlower openings 54, 58, the mandrel can be positioned within the pressurevessel central lumen 68 with a relatively tight fit between the upperand lower plates and the mandrel.

The shaping balloon 64 is formed from a membrane 70 having an upper edge72 and a lower edge 74. The upper edge 72 is sandwiched between theupper plate 52 and the central plate 60, while the lower edge 74 issandwiched between the central plate 60 and the lower plate 56. Theshaping balloon 64 when viewed from above preferably has a generallyring-like or circular shape. Shaping balloons according to the inventionmay be in various shapes and configurations, including configurationwhere multiple balloon envelopes are assembled around a perimeter toform a shaping balloon assembly. Substantially circular shapes such asthat depicted in FIGS. 2A-2E may be preferable for compressing stents.For stents having a relatively short length compared the width, such asthose configured for support of heart valve leaflets in a prostheticheart valve assembly, a shaping balloon may be formed in a toroidalshape. For example, in FIGS. 2A-2E, the shaping balloon 64 is formedsubstantially as the inner half of a toroid, and more specifically asthe inner half of a toroid with substantially circular cross-section,i.e., a torus.

A fluid lumen 76 passes through the central plate and is in fluidcommunication within the interior chamber 78 of the shaping balloon 64.A pressure vessel 50 according to the invention may have a pressuregauge fluidly connected to the balloon interior chamber 78 (e.g., viathe fluid lumen 76) for monitoring the pressure level therewithin. Theballoon interior chamber may be pressurized with a fluid, and maypreferably be a liquid for minimum compressibility. However, the ballooninterior chamber may alternatively be pressurized with a gas. Thepressurization of the balloon interior chamber may typically befacilitated by a balloon inflation device, such as that used forangioplasties (e.g., a syringe used to inflate the balloon) or otherpressure sources, such as a compressed air line or hydraulic line. Insome instances, the balloon inflation device may include its ownpressure gauge. Alternatively, a separate pressure gauge may be fluidlyconnected to the balloon interior chamber. Note that alternative devicesmay be used to pressurize the balloon interior chamber.

The pressure vessel 50 is depicted by itself in FIG. 3 . The balloon 64is in its unexpanded configuration, wherein the balloon inner opening 66has a diameter 80 a which is equal to or less than the diameters of theupper and/or lower openings 54, 58, so that the balloon 64 will notobstruct the pressure vessel central lumen 68 and will not interferewith the movement of the mandrel into and out of the pressure vesselcentral lumen 68. Note that even in the so-called “unexpanded”configuration, the balloon 64 may have some fluid therein.

A mandrel of the invention can be formed into any desired shape.Mandrels 32 a-32 e according to embodiments of the invention may havevarious profiles, such as those profiles 44 a-44 e depicted in FIGS.4A-4E, for their stent-support portions 42 a-42 e. FIG. 4A depicts amandrel 32 a having a substantially constant-diameter cylindricalprofile 44 a. FIG. 4B depicts a generally tapered mandrel 32 b with atapering profile 44 b along the length of the stent-support portion 42b. In FIG. 4C, a mandrel 32 c has a profile 44 c which is wider towardthe bottom, narrower in the middle, and wider again at the top of thestent-support portion 42 c. In FIG. 4D, a mandrel 32 d has a profile 44d which is narrower toward the bottom, wider toward the center, and thennarrower at the top of the stent-support portion 42 d. FIG. 4E depicts amandrel 32 e where the stent-support portion 42 e starts wide at thebottom, narrows further up, widens again further up, and then narrows atthe top. Note that mandrels of the invention may have detachableportions along their lengths to facilitate stent attachment and/orremoval from the mandrel. For example, as depicted in FIG. 4C, themandrel 32 c has a separation line 82 at the narrowest point, where anupper mandrel half 84 a can be separated from a lower mandrel half 84 bto facilitate stent removal and/or attachment.

A stent 10 is initially positioned on a mandrel 32, with the stent 10 ina substantially simple constant-diameter cylindrical configuration(i.e., a pre-shaped configuration), as depicted in FIG. 5 . Note thatthe stent 10 in this initial configuration has a maximum outer diameter86 which is less than the upper diameter 40 and/or lower diameter 36, sothat the stent 10 rests securely in the recessed stent-support portionand will not interfere with the mandrel 32 being slidingly advanced intothe pressure vessel (as depicted in FIG. 6 ). This initial positioningof the stent onto the mandrel may include sliding the stent over themandrel and partially crimping the stent to a slightly reduced profileso that its maximum outer diameter is less than the upper diameter 40and/or lower diameter 36. For a mandrel with removable portions, initialpositioning may include removing one or more of the removable portionsto permit the stent to slide onto the stent-support portion withminimal, or no, initial crimping. For example, initial positioning ofthe stent 10 may include removing the mandrel upper portion 38, slidingthe stent 10 over the mandrel central stent-support portion 42 from thetop, and replacing the mandrel upper portion 38. As another example,initial positioning of the stent 10 may include removing the mandrellower portion 34, sliding the stent 10 over the mandrel centralstent-support portion 42 from the bottom, and replacing the mandrellower portion 34.

In FIG. 6 , the mandrel 32 is fully seated within the pressure vesselcentral lumen 68, with the stent 10 and stent-receiving portion 42positioned longitudinally adjacent the shaping balloon 64, the mandrelupper portion 38 adjacent the upper plate 52, and the mandrel lowerportion 34 adjacent the lower plate 56. The shaping balloon 64 is in itsunexpanded configuration.

Fluid is introduced into the balloon interior chamber 78 via the fluidlumen 76 to expand the shaping balloon 64 to its expanded configuration.The pressure exerted by the shaping balloon 64 compresses the stent 10against the mandrel 32 to give the stent 10 its desired shape, asdepicted in FIG. 7 . The fluid is provided at a pressure sufficient tocompress the stent 10 to the desired shape. The pressure required forstent compressions/shaping will vary according to the particularapplication, including specifics such as the radial strength of thepre-shaped stent, etc. For example, a stent with more rigidcharacteristics may require higher fluid pressures for the balloon tocompress the stent to the desired shape. Pressures for use with theinvention may be in the range of about 75 to 150 psi, depending on theparticular application. Other pressures are also within the scope of theinvention.

After the stent 10 is compressed to the desired shape, the balloon 64can be deflated to its unexpanded configuration, and the mandrel 32 withshaped stent 10 thereon can be slid out of the pressure vessel 50. Tofacilitate stent removal, the mandrel may include one or moredetachable/re-attachable portions. For example, as depicted in FIGS. 8Aand 8B, the upper portion 38 of the mandrel 32 may be detachable and/orre-attachable from the stent-support portion 42. With the upper portion38 removed, as shown in FIG. 8B, the shaped stent 10 can be easily slidoff the top of the mandrel 32.

Note that the lower portion of the mandrel may similarly be detachableand/or re-attachable from the stent support portion. Additionally, themandrel stent-support portion 42 may itself have portions which aredetachable and/or re-attachable.

As depicted in FIG. 9 , the mandrel 32 may include a rigid inner portion86 with a coating 88 of a resilient material on the centralstent-support portion 42 which can be partially compressed. Theresilient coating 88 may provide some padding for a stent as it iscompressed into the mandrel 32. The resilient coating 88 may make itpossible for a prosthetic heart valve assembly to be compressed onto themandrel in its assembled form (e.g., with valve leaflets secured to thestent interior), with the resilient coating 88 providing a cushion toprotect the valve leaflets as the stent is compressed onto the mandrelto assume the desired shape.

A mandrel 32 of the invention may include one or more heating elements90, which may be used to apply heat to the mandrel 32 in order to setthe shape of a shape-memory stent being compressed, either alone or as apartially- or completely-assembled medical device (e.g., assembled heartvalve) into the form of the mandrel 32.

FIGS. 10A-10B depict a pressure vessel 50 with shaping balloon 64,wherein the shaping balloon 64 is formed from a flexible butsubstantially inelastic material, and may include substantiallynon-elastic cords and/or be formed from specific shape-enhancingmaterials (e.g., Kevlar, etc.) to further refine the shape. In FIG. 10A,the balloon 64 is substantially deflated and is radially retracted withrespect to the pressure vessel central lumen 68. In the deflatedcondition, the balloon 64 may have folds 92. In FIG. 10B, the balloon 64is expanded, and forms a pre-determined shape even without the presenceof a mandrel. Such a predetermined balloon shape may cooperate with theshape of the mandrel to provide even pressure and/or compression acrossa stent as it is compressed between the balloon and mandrel. Note thatthe choice of elastic v. non-elastic balloon materials depends on theparticular application.

The shaping balloon of the present apparatus may be fabricated fromvarious materials, including elastomeric and/or non-elastomericmaterials, depending on the particular application. For example,polyethylene (PE), polyethylene terephthalate (PET), and nylon may beused for balloons. If the device is to be used to shape-set memorymaterials such as nitinol, the balloon may preferably be formed ofmaterials resistant to the temperatures involved. Materials likeEthylene Propylene Diene Rubber (EPDM), TFE/Propropylene Rubber (FEPM),Silicone Rubber (VMQ) and Perfluorinated Elastomer (FFKM) may be optionsfor balloon materials. For example, if heat is to be provided, e.g.,from the mandrel or via the balloon itself (such as via hot fluid beingprovided therein), the balloon material may preferably be resistant tobeing damaged or otherwise compromised by the heat being provided.Alternatively, relatively cool fluid may be pumped into the ballooninterior to cool the balloon and prevent the balloon material from beingdamaged by the shape-set memory temperatures to which the stent is beingexposed.

Stents for use with the invention may be formed of various biocompatiblematerials. For a shape-memory material stent, the method may be variedto achieve shape setting when the stent is in the compressedconfiguration (i.e., with the shaping balloon expanded and compressingthe stent onto the mandrel). For example, after or during the step ofinflating the shaping balloon with sufficient pressure to cause theshaping balloon to expand to its expanded configuration, and while thestent is compressed against the mandrel (and prior to deflating theshaping balloon) it may be desirable to expose the stent to a desiredshape-setting temperature, and then to reduce the temperature to end theshape-setting process. Exposing the stent to the desired temperature mayinclude applying heat via heating elements, such as those depicted inFIG. 10 as elements 90, and reducing the temperature after setting theshape may include discontinuing power to the heating element(s).Exposing the stent to the desired shape-setting temperature may includeintroducing heated fluid into the interior chamber of the shapingballoon, with the heating fluid being provided at a temperature that isat or above the desired shape-setting temperature. Exposing the stent tothe desired reduced temperature may involve adding to the ballooninterior chamber fluid having a temperature that is at or below thedesired shape-setting temperature.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription and not of limitation. Therefore, changes may be made withinthe appended claims without departing from the true scope of theinvention.

What is claimed is:
 1. An apparatus for shaping stents, comprising: apressure vessel comprising upper and lower walls and a pressure vessellumen extending axially through the pressure vessel defined by upper andlower openings in the upper and lower walls, respectively, the pressurevessel further including an annular shaping balloon held between theupper and lower walls and positioned circumferentially about thepressure vessel lumen and defining an inner balloon opening, thepressure vessel defining a balloon inflation passage open to an interiorchamber of the shaping balloon which has an inflated configuration and adeflated configuration, wherein in the deflated configuration of theshaping balloon the inner balloon opening has a greater diameter thanboth the upper and lower openings so as not to extend into the pressurevessel lumen; and a mandrel having a mandrel longitudinal axis and astent-receiving portion between two opposite ends and having anon-cylindrical shape, the mandrel sized to be received co-axiallywithin the pressure vessel lumen, such that when a stent is positionedonto the stent-receiving portion of the mandrel and the mandrel isreceived co-axially within the pressure vessel lumen, inflation of theshaping balloon causes the balloon opening to compress the stent againstthe stent-receiving portion of the mandrel and deform the stent into thenon-cylindrical shape of the stent-receiving portion.
 2. The apparatusof claim 1, wherein the stent-receiving portion of the mandrel comprisesan inner shape which is formed from rigid, non-deformable material andhas an outer surface formed from flexible material.
 3. The apparatus ofclaim 2, wherein the stent-receiving portion of the mandrel is shaped toform a stent of a prosthetic heart valve with leaflets, wherein theflexible material on the mandrel helps prevent damage to the leaflets.4. The apparatus of claim 1, wherein the mandrel comprises an uppermandrel plate, a lower mandrel plate, and the stent-receiving portiontherebetween, wherein the upper mandrel plate has an upper diametersized to fit tightly into the upper opening and the lower mandrel platehas a lower diameter sized to fit tightly into the lower opening, andthe stent-receiving area comprising one or more areas of reduced radialdiameter smaller in diameter than at least one of the upper diameter orlower diameter.
 5. The apparatus of claim 4, wherein the stent-receivingarea is circular in cross-section but has varying diameters along alongitudinal length thereof.
 6. The apparatus of claim 4, wherein atleast one of the upper mandrel plate and the lower mandrel plate areconfigured to be releasably attached and re-attached to thestent-receiving portion.
 7. The apparatus of claim 1, wherein themandrel has a separation line such that an upper mandrel half can beseparated from a lower mandrel half to facilitate stent removal and/orattachment.
 8. The apparatus of claim 1, wherein the mandrel includesone or more heating elements embedded therein.
 9. The apparatus of claim1, further including a pressure gauge fluidly connected to the ballooninterior chamber.
 10. The apparatus of claim 1, wherein the pressurevessel upper wall is defined by an upper plate, and the pressure vessellower wall is defined by a lower plate, and the pressure vessel furtherhas a central plate comprising a central plate opening defining an innerperimeter, wherein the upper plate and lower plate and central plate arestacked together with the central plate positioned between the upperplate and the lower plate, and the shaping balloon comprises an upperedge and a lower edge, wherein the upper edge of the shaping balloon issandwiched between an upper surface of the central plate and a lowersurface of the upper plate, and the lower edge of the shaping balloon issandwiched between a lower surface of the central plate and an uppersurface of the lower plate such that the central plate opening faces theinterior chamber of the shaping balloon, and wherein the ballooninflation passage passes through the central plate and central plateopening.
 11. An apparatus for shaping stents, comprising: a pressurevessel having rigid walls holding an annular shaping balloon formed froma flexible but substantially inelastic material, the shaping balloonhaving a radially inwardly facing balloon opening, the balloon openinghaving a pre-determined non-cylindrical shape when the shaping balloonis inflated, the pressure vessel defining a balloon inflation passageopen to an interior chamber of the shaping balloon; and a mandrelcomprising a non-cylindrical stent-receiving portion, wherein themandrel is sized and configured to be slidingly advanced into thepressure vessel to a position where the stent-receiving portion ispositioned within the balloon opening, and wherein the pre-determinedshape of the balloon opening of the inflated shaping balloon conforms tothe non-cylindrical stent-receiving portion, such that when a stent ispositioned onto the stent-receiving portion of the mandrel and themandrel is received within the pressure vessel, inflation of the shapingballoon causes the balloon opening to compress the stent against thestent-receiving portion of the mandrel and deform the stent into thenon-cylindrical shape of the stent-receiving portion.
 12. The apparatusof claim 11, wherein the stent-receiving portion of the mandrelcomprises an inner shape which is formed from rigid, non-deformablematerial and has an outer surface formed from flexible material.
 13. Theapparatus of claim 12, wherein the stent-receiving portion of themandrel is shaped to form a stent of a prosthetic heart valve withleaflets, wherein the flexible material on the mandrel helps preventdamage to the leaflets.
 14. The apparatus of claim 11, wherein themandrel comprises an upper mandrel plate, a lower mandrel plate, and thestent-receiving portion therebetween, wherein the upper mandrel platehas an upper diameter sized to fit tightly into the upper opening andthe lower mandrel plate has a lower diameter sized to fit tightly intothe lower opening, and the stent-receiving area comprising one or moreareas of reduced radial diameter smaller in diameter than at least oneof the upper diameter or lower diameter.
 15. The apparatus of claim 14,wherein the stent-receiving area is circular in cross-section but hasvarying diameters along a longitudinal length thereof.
 16. The apparatusof claim 11, wherein the mandrel has a separation line such that anupper mandrel half can be separated from a lower mandrel half tofacilitate stent removal and/or attachment.
 17. The apparatus of claim11, wherein the mandrel includes one or more heating elements embeddedtherein.
 18. The apparatus of claim 11, further including a pressuregauge fluidly connected to the balloon interior chamber.
 19. Theapparatus of claim 11, wherein the shaping balloon includes non-elasticcords embedded therein.
 20. The apparatus of claim 11, wherein thepressure vessel upper wall is defined by an upper plate, and thepressure vessel lower wall is defined by a lower plate, and the pressurevessel further has a central plate comprising a central plate openingdefining an inner perimeter, wherein the upper plate and lower plate andcentral plate are stacked together with the central plate positionedbetween the upper plate and the lower plate, and the shaping ballooncomprises an upper edge and a lower edge, wherein the upper edge of theshaping balloon is sandwiched between an upper surface of the centralplate and a lower surface of the upper plate, and the lower edge of theshaping balloon is sandwiched between a lower surface of the centralplate and an upper surface of the lower plate such that the centralplate opening faces the interior chamber of the shaping balloon, andwherein the balloon inflation passage passes through the central plateand central plate opening.